The present invention relates to an optical disk device which records data upon an optical disk such as a DVD-R, a DVD-RW, a DVD-RAM, a CD-R, a CD-RW, or the like.
Optical disk devices which record data upon recording media are per se generally known and popular. Such a recording medium is an optical disk such as a DVD-RW, a DVD-RAM, a CD-R, a CD-RW, or the like. As is per se well know, the recording process of data upon such an optical disk, marks which correspond to the data to be recorded are formed upon tracks of the optical disk in order. The optical disk device irradiates pulse modulated laser light upon the tracks of the optical disk, and thereby records the data.
Furthermore, with an optical disk device according to the prior art, when recording data upon the optical disk, in order to obtain the optimum recording power of the laser light which is irradiated upon the optical disk, a well known OPC is performed. The laser light is pulse modulated when recording data, as described above. The optimum recording power which is obtained by OPC is the peak power of the laser light which is being pulse modulated. The bottom power (the bias power) of the laser light which is being pulse modulated is the reading power which is irradiated upon the optical disk during normal replay. When recording data, in order to control the power of the laser light which is irradiated upon the optical disk to the optimum power for recording, it is desirable to detect the peak power of the laser light which is actually being irradiated upon the optical disk is detected, and to perform control based upon this detected value. Power control methods for, during recording, controlling the power of the laser light which is being irradiated upon the optical disk to the optimum recording power are disclosed in, for example, Japanese Laid-Open Patent Publication 2003-178452, Japanese Laid-Open Patent Publication H11-250459, Japanese Laid-Open Patent Publication 2001-357529, and Japanese Laid-Open Patent Publication 2004-55115.
Furthermore, when recording data upon the optical disk, the optical disk device performs various types of servo control, such as focus servo control in which the laser light is condensed upon the recording surface of the optical disk, tracking servo control in which the laser light is irradiated upon the center of a predetermined track of the optical disk (the center of the track upon which the marks are formed), and the like. This focus servo control is a type of control in which, based upon a focus error signal which is obtained by detecting the light reflected from the optical disk, an objective lens of the pickup head is shifted to and fro in the direction towards and away from the optical disk. And this tracking servo control is a type of control in which, based upon a tracking error signal which is obtained by detecting the light reflected from the optical disk, the pickup head main part, or the objective lens of the pickup head, is shifted in the radial direction of the optical disk.
With an optical disk device, if, during data recording, the focus servo control or the tracking servo control is performed based upon a focus error signal or a tracking error signal which is sampled at the period at which the laser light, which is being pulse modulated, is irradiated upon the optical disk, then these servo control processes are not performed adequately, and the operation becomes unstable. Thus, with a prior art type optical disk device, the servo control when recording data is performed by so called sampling servo control. This sampling servo control is a type of control in which sampling of the signal which is used in the servo control, such as the focus error signal or the tracking error signal or the like, is started along with the start of the sampling period, and this signal which is used for the servo control is held along with the end of this sampling period. The sampling period is set to be within the period from the completion of formation of one mark upon the optical disk, to the start of formation of the next mark.
However, with a prior art optical disk device, the above described sampling period is fixed, and bears no relationship to the type of the optical disk. For example, the start timing of the sampling period may be set after a first time period which is determined in advance has elapsed from the falling edge of NRZI, which is the recording signal (the end of the mark period), while the end timing of the sampling period may be set after a second time period which is determined in advance has elapsed from the rising edge of NRZI. On the other hand, the optical disk device irradiates the pulse modulated laser light based upon a write strategy, according to the type of optical disk upon which the data is to be recorded. As is per se well known, for each type of optical disk, a write strategy is a specification for the pulse modulation of the output of the laser during recording. Due to this, according to the type of the optical disk upon which the data is to be recorded, there is a period for which the laser light which is being irradiated upon the optical disk is to be pulse modulated. In other words, the optical disk device performs sampling of the signals which are used for servo control, such as the focus error signal and the tracking error signal and the like, at the period at which the laser light which is irradiated upon the optical disk is pulse modulated, according to the type of the optical disk upon which the data is to be recorded.
The object of this invention is to provide an optical disk device with which servo control is performed adequately when recording data, irrespective of the type of optical disk upon which the data is to be recorded.